1. Field of the Invention
The present invention relates to an image forming method and apparatus for effectively supplying developer, and more particularly relates to a developer container containing two-component developer, an image forming apparatus including the developer container to supply the two-component developer to a developing unit, and methods of packing the two-component developer and of determining a condition of the two-component developer packed in the developer container.
2. Discussion of the Related Art
A two-component developer includes toner and carriers and is generally contained in a developer container. As an image forming operation is repeated, a coated layer on a surface of the carrier in the developer container may be damaged by abrasion due to aging and/or by adhesion of a toner resin and additives thereto. Such a carrier cannot effectively charge toner and may gradually deteriorate, which can cause fogging on the background of an image and toner scattering to an image when the condition of the carrier falls below an acceptable level. Therefore, a technical representative visits a user on a regular basis to replace the developer accommodated in a background image forming apparatus. Accordingly, a unit price of a copy has increased to compensate for the large amount of maintenance costs.
A background image forming apparatus has employed a process that can regularly perform automatic replenishment and discharging of carriers as well as toner. The above-described process is one type of a process known as “trickle development.” The above-described process stores and supplies carrier and toner separately, which requires space for respective storing units and respective replenishing mechanisms for both toner and carrier and may increase the cost and size of the entire image forming apparatus.
A different background image forming apparatus includes spiral containers with respective opening parts for replenishment for discharging stored developers and have a projection streak part that is provided so as to project inward from at least a container internal wall and be spiral toward the opening part for replenishment. In such a device a developer receiving device is replenished with a developer carried by the projection streak part as the spiral containers rotate, and the developer contains a 1 pt. wt. carrier and a 1 to 30 pts. wt. toner, the true specific gravity of the carrier being 2.5 to 4.5.
Accordingly, a developer replenishing developing unit serving as a replenishing mechanism may not provide toner scattering even in use for a long period of time and can maintain a stable amount of toner charge in the developing unit and provide high image density uniformity and gradation, and thereby high quality image without fogging thereon can be obtained.
Further, a different background image forming apparatus includes a developer supplying kit that serves as a replenishing mechanism and is detachably attached to the background image forming apparatus. The developer supplying kit includes a developer storing part for storing the developer in the inside thereof, a discharging opening mounted on the developer storing part for discharging the developer, and an agitating member arranged rotatably in the inside of the developer storing part. The agitating member includes a shaft part for rotatably holding the agitating member on the developer supplying kit, and an agitating blade formed on a flexible member and attached to the shaft part. The agitating blade slides and scratches the inner wall face of the developer supplying kit. In the developer supplying kit for agitating and conveying the developer, the developer includes a mixture of toner and substantially spherical spacer particles. An average particle diameter (D50) of the spacer particles is larger than a weighted average particle diameter (D4) of the toner.
With the above-described structure, the occurrence of coarse particles caused by image inferiority when the developer is transported to a developing unit may be suppressed.
The above-described two background image forming apparatuses have employed a method in which a developer or a carrier is added to toner accommodated in a bottle cartridge for replenishment so as to supply the toner while rotating the bottle cartridge.
FIG. 1 shows a schematic structure of a bottle cartridge 33 employed in the above-described background image forming apparatuses in which the above-described method is used.
In FIG. 1, the bottle cartridge 33 includes a cylindrical bottle 42 having a containing portion therein and a cap 34. The containing portion of the cylindrical bottle 42 includes a spiral protrusion or spiral groove on an internal surface thereof and contains toner therein to be supplied to a developing unit 39.
When the bottle cartridge 33 is connected to a replenishing mechanism (not shown), a bottom surface of the cylindrical bottle 42, which is an end portion opposite to the cap 34, and a bottle drive motor 38 are engaged with each other. At the same time, the cap 34 is fixedly attached to the replenishing mechanism. When a lever 37 mounted on the cap 34 is pulled down, an opening (not shown) of the cylindrical bottle 42 is opened. Further, when the bottom surface of the cylindrical bottle 42 and a drive shaft (not shown) of the bottle drive motor 38 are engaged, a shutter pin 41a mounted on a shutter 41 is guided in an upward direction along a slope of a protruding portion 40 of the developing unit 39. Thereby, the shutter 41 opens to open an outlet 36.
Generally, when a mixture of toner and carrier is supplied from a rotary bottle such as the cylindrical bottle 42 having a spiral groove on an internal surface thereof, the toner has been conveyed to an outlet of the cylindrical bottle 42 while being agitated in the cylindrical bottle 42.
However, when the above-described bottle cartridge 23 includes a resin material or other material having rigidity, toner and carrier contained in the bottle cartridge 23 may be separated so as to supply the carrier before or after the toner. Since in such a case developer cannot have a stable amount of toner, the toner density in the developing unit cannot be controlled stably and, as a result, defective images may be reproduced.
Specifically, the carrier having a greater specific gravity may subdue or sink to a lower portion of the internal surface of the cylindrical bottle 42 while being agitated. Since the carrier is held in contact with or located close to the internal surface, the drive force of the cylindrical bottle 42 can be transmitted to the carrier easier than to the toner gathering in a center portion of the cylindrical bottle 42, and thereby the carrier is conveyed to the outlet of the cylindrical bottle 42 along the spiral groove and selectively supplied before the toner. As a result, the toner density control in the developing unit 39 becomes unstable, thereby causing production of defective images.
Further, as the bottle is rotated, the toner separated from the carrier may be coagulated in the bottle, which can also result in defective images having white spots.
Since the above-described background image forming apparatuses use toner and carrier, an increase of costs cannot be avoided.
Further, since a large amount of carriers is replenished and used, the cost for consumables including toner and carrier may increase and the used carrier may further contaminate the environment.
On the other hand, when a suction type toner supplying unit is employed, toner is filled to a container including a flexible material such as a vinyl and is sucked by a pump to be supplied to a developing unit. Such a suction type toner supplying unit cannot stably supply the toner to the developing unit when the toner is fully packed in the container. In other words, the container is required to include an air space to smoothly supply the toner therefrom. However, when the dimension of that air space becomes greater, the amount of toner packed may be smaller or the dimension of the image forming apparatus may be greater.